In the area of thermal printers, it is well-known that the use of such printers is increasing for certain operations that require a reduction in noise levels and at a reasonable cost. While development work is continually progressing to increase the speed of operation with minimum maintenance or care of the equipment, it is seen that improvements are being made to provide a higher quality print with a reduced number of thermal elements.
In the case of thermal printers, it is necessary to minimize the complexity of the thermal print head and the associated electronic controls. In certain prior art printers, it has been common practice to provide a thermal print head having a plurality of thermal printing elements on the surface of the head and wherein selected elements are energized to provide printing on thermal paper or like record media with the print head operating in a stationary or fixed position relative to the printer frame. The thermal printing elements on the print head may take the form of pads or contact surfaces in the shape of characters and connected by conducting runs to side or edge connectors. A flexible flat ribbon-like cable is normally used to connect the power and/or control circuitry with the pads or contact surfaces on the print head and the individual leads or wires of the cable may include end connectors or terminals for contact with the print head pads.
In the field of ink ribbons for printers, a ribbon supply spool and a ribbon take-up spool have been provided on opposite sides of a typing or printing station, together with means for reversing the direction of travel of the ribbon for repeated use thereof in an arrangement for the purpose of obtaining longer ribbon life. Also, the ink ribbon has been made to travel along a line of printing wherein the spools are positioned beyond the ends of the printing line and the ribbon is caused to travel at an angle relative to the print line to utilize a greater portion of the ribbon width. However, in the case of certain high-speed printers, a ribbon substantially as wide as the line of printing may be used and caused to travel in a direction normal to the print line and along with the record media. Additionally, it has been common to provide ink carrying or containing means operably associated with the ribbon for maintaining or replenishing a supply of ink therein for proper and extended-life printing operations.
In present day printers, it is also common practice to provide and use a ribbon cassette carrying an endless ribbon which is caused to be driven past a printing station, and wherein the printing ribbon is either a pre-inked and disposable ribbon or a ribbon which is to be continuously or frequently re-inked during the printing operation. The ribbon cassette itself may be of the stuffing-box type wherein the ribbon is contained within the cassette in random manner and such ribbon is unfolded at the cassette exit and caused to be driven past the printing station and then guided back into the cassette to be folded again in random manner therein. Additionally, a ribbon may be utilized in a Mobius loop configuration within the cassette, the ribbon may be maintained in substantially continuous contact with an inking core or like member, or the ribbon may have a plurality of coils thereof around a central core for controlled inking or re-inking of the ribbon.
More recently, development work in thermal printers has included a shuttling-type print head having approximately 20% of the number of print elements compared to the number of elements on a fixed or stationary head. A ribbon associated with a print head and used for transferring material from the ribbon and onto plain paper may be of the thermal transfer type or of the magnetic thermal transfer type, dependent upon the particular application.
One of the problems encountered with the shuttling print head is that of smudging the thermal paper on which the printed image is formed by reason of pressure or contact between the print head and the paper or between the print head and the platen during travel of the print head across the printer. Since it is common practice to print in one direction of travel of the print head, it is deemed to be an improvement over prior printing apparatus and is advantageous to eliminate or at least reduce the pressure of the print head against the thermal paper and against the platen during the return cycle of the print head and its carriage.
Another of the problems encountered with a shuttling print head involves the thermal printer that utilizes the thermal ribbon for transferring material from the ribbon onto the plain paper. In the case of the thermal transfer ribbon, the printing cycle needs to accommodate the moving print head and the moving ribbon in timed relationship so as effect a complete transfer of the material to the paper. While thermal transfer ribbons have been used both in impact and in non-impact printers, it is important that the ribbon be contained and controlled in a manner to effect sharp and well-defined printed characters.
Representative documentation in the field of ribbon cassettes includes U.S. Pat. No. 3,617,010, issued to D. R. Coy on Nov. 2, 1971, which discloses a magnetic tape carried on a platform of a spool and payed out from the center of the coil. The tape travels past a head and through the nip of a capstan and a pressure roller for returning as an outermost winding on the coil.
U.S. Pat. No. 2,734,615, issued to J. H. Van Wallendael on Feb. 14, 1956, discloses guide means for directing the ribbon along a diagonal across the print line.
U.S. Pat. No. 3,981,387, issued to J. A. Gottschlich on Sept. 21, 1976, discloses a reel with a ribbon having an inner turn unwinding from the coil over a guide rod and an outer turn rewinding on the coil with the ribbon being driven by a feed gear and an idler gear.
U.S. Pat. No. 3,995,731, issued to H. R. Miller et al. on Dec. 7, 1976, shows the ribbon unwinding from the inner portion of the coil and rewinding on the outer portion of the coil.
U. S. Pat. No. 4,011,934, issued to B. I. L. Ploby et al. on Mar. 15, 1977, shows a ribbon being guided to extend obliquely between the printing device and the paper.
U.S. Pat. No. 4,071,132, issued to J. M. Steinke et al. on Jan. 31, 1978, discloses an endless ribbon passing from the inside of a wrapped portion of a roller over a guide member and then back onto the outside of the wrapped portion.
U.S. Pat. No. 4,209,261, issued to D. W. Bell on June 24, 1980, discloses a cassette with the ribbon directed at an angle in its travel past the printing station.
U.S. Pat. No. 4,279,390, issued to E. S. Wu on July 21, 1981, shows a ribbon being guided by a shaft from a supply reel at an angle therefrom, past a print station, and onto a take up reel.
And, IBM Bulletin Vol. 19, No. 10, March 1977, page 3817, shows a ribbon directed at an angle to the print line for distributing print activity over the entire surface area of the ribbon.